Heart rate monitor



FIG. 1 is a front, top perspective view of a heart rate monitor showing our new design;

FIG. 2 is a rear, bottom perspective view thereof;

FIG. 3 is a top view thereof;

FIG. 4 is a bottom view thereof;

FIG. 5 is a left side view thereof;

FIG. 6 is a right side view thereof;

FIG. 7 is a rear view thereof; and,

FIG. 8 is a front view thereof.

The dot-dash broken lines depict the boundaries of the claimed design and form no part thereof. The dash-dash broken lines depict portions of the heart rate monitor that form no part of the claimed design. 

CLAIM The ornamental design for a heart rate monitor, as shown and described. 